1. Field of the Invention
The present invention relates to a scroll compressor having a vacuum preventing structure, and more particularly, to a scroll compressor having a vacuum preventing structure capable of preventing a vacuum of the compressor by making a gas of a discharge pressure side backflow toward a suction pressure side during the abnormal operation such as the pump down or clogging of an expansion valve.
2. Description of the Background Art
In general, a compressor changes mechanical energy into latent energy of compression fluid, and is classified into a reciprocating type compressor, a scroll type compressor, a centrifugal type compressor and a vane type compressor.
Among them, unlike the reciprocating type compressor using linear reciprocation of an opening/closing member, the scroll type compressor sucks, compresses and discharges a gas by using a rotation body like the centrifugal type compressor or the vane type compressor.
FIG. 1 is a longitudinal sectional view showing the conventional scroll compressor, and FIG. 2 is an enlarged view showing an important part of FIG. 1.
As shown therein, the conventional scroll compressor includes: a casing 11 forming a receiving space therein; a compression part 31 received and installed in the casing 11, for compressing a refrigerant; and a motor part 21 for supplying a driving force to the compression part 31.
A suction pipe 13 and a discharge pipe 15 for sucking and discharging a refrigerant is formed at one side of the casing 11, and an upper frame 17 and a lower frame 19 are separately and vertically installed in the casing in order to support the compression part 31 and the motor part 21.
The compression part 31 includes a fixed scroll 33 having a wrap 34 of an involute shape and fixedly installed at the upper frame 17 and an orbiting scroll 35 having a wrap 37 of an involute shape, coupled with the fixed scroll 33 to reciprocally form a compression space (S), and compressing a refrigerant while performing the relative motion with respect to the fixed scroll 33.
A high/low pressure separation plate 39 for separating the inside of the casing 11 into a discharge pressure space (S2) and a suction pressure space (S1) is coupled with the fixed scroll 33.
The motor part 21 includes a stator 23 fixedly installed in the casing 11 and a rotor 25 rotatably received and installed in the stator 23 on the basis of a rotary shaft 27 having an eccentric portion 28 at its one side.
Meanwhile, in case of the pump down or in case that an expansion valve is clogged, the suction pressure space (S1) becomes in a high vacuum. At this time, the constituting parts of the compressor can be damaged by fire or broken.
To prevent this problem, there is provided a vacuum preventing device 41 in the conventional art.
The vacuum preventing device 41 includes: a back pressure passage 43 formed at a predetermined depth along a radial direction from a side surface of the fixed scroll 33; a discharge pressure hole 44 formed at an upper portion of the back pressure passage 43 to make the back pressure passage 43 communicate with the discharge pressure space (S2); a middle pressure hole 45 formed at a lower portion of the back pressure passage 53 to make the back pressure passage 43 communicate with the compression space (S); a piston 47 slidably received in the back pressure passage 43, for opening or closing the discharge pressure hole 44; a spring 48 for applying an elastic force at the piston 47 such that the piston 47 can move from its one side to a position where the piston 47 opens the discharge pressure hole 44; a stopper 46 inserted into an inlet side of the back pressure passage 43; and a fixing pin 50 for fixing the stopper 46 to prevent separation of the stopper 46.
A suction pressure hole 49 for connecting the back pressure passage 43 with the suction pressure space (S1) is penetratingly formed at the center of the stopper 46. A pin hole 36 for inserting and coupling the fixing pin 50 into the fixed scroll 33 is formed at the fixed scroll 33.
However, in the conventional scroll compressor having such a construction, the piston and the spring are mounted in the back pressure and the stopper is fixed by inserting the fixing pin into the pin hole, thereby causing an assembly to be difficult. In addition, since the pin hole is positioned at an outer edge of the fixed scroll 33, intensity around the pin hole is low and therefore the fixed scroll can be easily damaged.
In addition, a refrigerant gas in the discharge pressure space (S2) flows into the back pressure 53 through the discharge pressure hole 44, and the refrigerant gas having flowed into the back pressure 53 flows into the suction pressure space (Si) through the suction pressure hole 49. At this time, the high temperature refrigerant gas receives flow resistance, thereby stopping the driving of the motor part 21. Accordingly, it takes relatively much time to release the vacuum of the scroll compressor.